Modular irrigation control system

ABSTRACT

A central control unit generates starting signals which are distributed to a number of remote zone control units, each of which is programmed successively to actuate selected ones of a respective set of valves in accordance with a preselected schedule. A chain of zone control units may be triggered in succession, each by a signal from the preceding such unit, to carry out its assigned schedule when the schedule assigned to the preceding zone control unit has been completed. Both the central and the zone control units are made to respond automatically and positively to various events such as a power failure, rain, excessive ground moisture, and the actuation of the valves. A simple method of sending signals in both directions between a central control unit and a zone control unit over a single pair of wires is also provided to actuate the system components remotely.

United States Patent 1 3,599,867

[72] Inventors David E- GIiSWOld 3,440,434 4/1969 Yates et al. 239/70 Corona Del Mar; 3,524,471 8/1970 Bresser 239/70 X orllsthan D. Lrklns, Costa Mesa, both of, Primary Examiner uoyd L. King [2]] pp No ,7 6 Att0rney-Fowler, Knobbe & Martens [22] Filed Nov. 12, 1969 a [45] Patented Aug. 17, 1971 [73] Ass'gncc Grisvmld ABSTRACT: A central control unit generates starting signals Santa Amcan which are distributed to a number of remote zone control units, each of which is programmed successively to actuate [54] MODULAR IRRIGATION CONTROL SYSTEM selected ones of a respective set of valves in accordance with a 16 claims 26 Drawing Figs preselected schedule. A chain of zone control units may be triggered in succession, each by a signal from the preceding [52] US. Cl 239/63, Such unit, to carry out its assigned schedule when the Schedule A01 assigned to the preceding zone control unit has been [51] Int. Cl g completed [50] Field olSearch 239/63,70 Both the central and the Zone control units are made to [56] R f r nces Cited respond automatically and positively to various events such as e e e UNITED STATES PATENTS tuation of the valves. A simple method of sending signals in 2,821,434 1/1958 Hunter et al 239/63 X both directions between a central control unit and a zone con- 2,989,667 6/ 196] Swink 239/63 X trol unit over a single pair of wires is also provided to actuate 3,063,643 1 1/1962 Roberts 239/70 the system components remotely.

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SHEET 13 HF 1 INVENTORS DAV/0 1 GE/SWOLD FOWL 5e; KNOBBE a Mnerlsws 1 MODULAR IRRIGATION CONTROL SYSTEM TABLE OF CONTENTS A. ABSTRACT OF THE DISCLOSURE Pg. l B. BACKGROUND OF THE INVENTION 1 C. SUMMARY OF THE INVENTION l D. DESCRIPTION OF THE DRAW- 3 E. DESCRIPTION OF AN EXEMPLARY SYSTEM INCORPORATING THE IN- VENTION 4 1. Typical Application of the System 4 2. Possibilities of the Series Start Feature 5 3. Selecting a Particular Set of Schedules and Schedule Starting Times 6 4. Organization and Operation of the Exemplary System 7 (a) Introduction 7 (b) The Control. Section of the Zone Control Unit 7 (1) In General 7 (2) Stepping the Valve Control afer. Switch 8 (3) Producing a. Variable Delay for SteppingtheSwitch 9 (4) Initiating av Schedule in Response to 8. Starting Signal 12 (c) The Starting-Signal Generator of the Central Control-Unit; l3 (1) In General; l3 (2) Shaping the:Starting..Signal l4 (3) Timingthe-Stanting Signal"... 15 (4) Driving the Day and. Hour Index Wafer :Switohes 16 (d) Information-Feedback 17 (0) Schedule Abort- Zl (f) The Tensliomoter-Circuit 22 (g) Moisture Cut Off; 23 (h) The Rain CutOff-Circuit 24 (i) The Series Start Cirouit- 24 B. BACKGROUNDJQF-IHEINVENTION The present invention .is directed to controlling the irrigation of large areas, such as-gnlfrcourses. The areas which need to be controlled vary-considerably. Thus;-controls -of:different sizes and complexitiesarerequiredrinrdifferentdocations, depending-upon the size and acomplexity of the-area which is to be irrigated. This variation maltes'it difficult to mass-produce controls due to the need to'manufacture and merchandize controls having different capabilities. A useful technique which permits taking advantage. of the economies of'mass production is to modularize thetcontrol so thatachanges =in1the magnitude of jobs can be.accommodated by increasing the number of modulesratherthan by increasingthe size and complexity of thecontrol-itsclf.

One approachto'modularizing.anirrigation control is to use a single central controlunit-antlealarge'number: of remote zone controlunits, all.of-which-are.actuatedconcurrently by a single starting signalfromtthecentrahcontrolunit. Thus,,at selected times during.each=day, all-of'the remote-control units can be actuated, and they .'in -tum actuate their associated group of valves in succession. This techniquerhasrthe'disadvantage that all-of the-vaivesaresturnedonatzthe same time, at least when the remotezone control unitsarc initially actuated and therefore a very heavytdemand.isrmadetonthe-supply-of water to the valves. Thus, -to-t-a ;certain extent,- theeconomy that has been gained through modu'larization of controlsis lost by the need to-increase the sizemf'the waterconduit-which is run to the valves.

C. SUMMARY-OF THEINION The water supply;problemarcferred'to above-is not inherent when a.-single;,central: controi'unitds-usedibecause itsoutputs can be serialized, so .that the.-.several :valvesin xthe field are turned on in .succession. A.1typical..system of this type is described in YatesiU;S.:'Pat..-No..324409434.-

The water supply problem.isinherentainathe modular approach.- because usualLy-only' onetcontroLchannel is run. from the central controltunittoall of the remote zone control units Col.

actuating their associated valves. in this so that, as successive starting signals are sent out, all of them are turned on in unison. Thus, at least initially, all of the remote valves draw water at the same time. in accordance with an important feature of the present invention, a plurality of remote zone control units are actuated in response to starting signals from a central controlunit. However, only a portion of them are turned on directly by the starting signals from the central unit, and therefore only those valves which are controlled by that portion of the remote units draw power at the same time. This initially actuated group of zone control units in turn actuates a subsequent or second group of zonecontrol units when members of the first group have completed way, even though only a few wires are run from the central control unit to the zone control units, and thus a large saving in wire costs is effected, this saving, as well as the saving effected through modularization is not achieved at the cost of excessive demands being placed on the water supply.

In keeping with this aspect of the invention, the central control unit generates starting signals at selected hours of selected days. Zone control units are arranged in one or more chains, with each chain including at least two individual zone control units, each responsive to a starting signal successively to actuate selected ones of a respective set of valves for selected periods of time in accordance with a preselected schedule and each zone control unit generating a starting signal when the selected actuation of the last of its associated set of valves has been completed. The first zone control unit in each chain receives a starting signal from the central control unit and subsequent zone control units in each chain are made to receive the starting signal produced by the immediately preceding zone control unit in the chain. in this way, successive zone control units and their associated valves in each chain are ac-. tuated in response to the completion of a schedule by the preceding zone control unit in that chain.

in accordance with another feature of the invention, a zone control unit includes a switching device which is initially advanced by a locally generated control signal in response to a remotely generated starting signal so as to advance the switching means to the first of a series of states, or positions, in which it is operative to actuate the first of its associated set of valves for a selected period of time. The switching means is then advanced through the remaining ones of its intermediate states or positions by means of a timing device which is operative to leave the switching means at each of its intermediate states for a preselected period of time. This arrangement permits the remotely located zone control unit to execute its particular schedule independently from the central control unit, except for the initial starting signal which sets the zone control unit into operation. In accordance with yet another feature of the invention, the starting signal is blocked after it has set the zone control unit into operation so as to prevent the same starting signal from triggering the zone control unit more than once.

The schedule of operations wi.f"h the zone control unit is capable of executing in response to a single s'taing signal is made quite extensive and flexible by means of another feature of the invention, whereby a schedule is made to include several cycles of valve actuation separated by delay periods. Respective ones of the valves associated with a given zone control unit are actuated successively during each of the several cycles and the length of time during which a given valve is actuated may be made different during each of the differentcycles. The delay periods between cycles are also made variable so as to allow the water which has been dispensed during the preceding cycle to be absorbed in the ground. Optionally, a zone control unit may have associated with it a moisture-sensing device which is operative to terminate a schedule which is in progress in response to excessive moisture in the ground. In keeping with this optional feature of theinvention, this can occur only during one of the delay periods between cycles so as to insure that all of agiven zone covered. by a particular set of valves is approximately equally watered, which would not be the case if a cycle were terminated after the actuation of only a portion of the total number of valves associated with the zone control unit.

In accordance with yet another feature of the invention, a schedule which is in progress is also terminated when power to the zone control unit is temporarily interrupted. This termination of a schedule in progress occurs automatically when power returns and makes possible the termination of a schedule in progress at any time that this is desired by interrupting the supply of power to the zone control unit from the central control unit, a feature which is also provided.

In addition to making the zone control units responsive to signals from the central control unit, means are also provided for making the central control unit responsive to signals fed back to it from the zone control units. Specifically, in keeping with this aspect of the invention, the irrigation system is supplied with water under pressure by means of a central pump which is controlled by the central control unit in response to signals sent to it from the zone control units, these signals indicating that a valve has been actuated. In this way, the central pump is on only when it needs to be on, that is when one of the valves to which water is to be supplied has been opened. At all other times the central pump may be turned off. Actually, in the case where a schedule is in progress and several valves are actuated in succession, it becomes undesirable to turn off the water pump during the very brief intervals between the actuation of the valves, these intervals being due to the finite time required for the switching device in the zone control unit to advance from a given one of its states to the next. Accordingly, means are provided in the zone control units to simulate the presence of a load similar to the electrical circuits of the valves during the switching intervals so as to keep the pump actuated continuously during a schedule.

It is an important feature of the present invention that the starting signals sent from the central control unit to the zone control units and the pump control signals sent from a given zone control unit back to the central control unit are transmitted over a single pair of wires. The manner in which the bidirectional transmission of signals on a single pair of wires is achieved is the sole invention of Jonathan D. Likins and is covered in a copending application filed by him and assigned to the assignee of the present application. However, the combination of the method of signal transmission and the irrigation system disclosed herein is the joint invention of David E. Griswold and Jonathan D. Likins and is claimed in the present application. In accordance with this feature of the invention, signals are transmitted in both directions between a central control unit and a given zone control unit over a pair of wires. An alternating current source in the central control unit is connected in series with one of the wires. Both the central control unit and the zone control unit is provided with means for sensing current flow through the wires in a respective one of mutually opposite directions. Also providing in each unit is a switching means for completing a respective circuit through the wires and through the sensing means in the other unit, the circuit completed by the switching means in a given unit being capable of carrying current only in the direction sensed by a sensing means in the other unit. A starting signal is produced in the central control unit by means which closes the switching means in that unit at selected hours of selected days. This completes a circuit through the sensing means in the zone control unit which also includes means for successively actuating its valves in accordance with a preset schedule in response to the detection of current by its sensing means. The zone control unit also includes means for closing its switching means while any of the valves controlled by the zone control unit is being actuated. Closure of this switching means completes a circuit through the sensing means in the central control unit, which additionally includes means for actuating the central pump in response to the detection of current by its sensing means.

D. BRIEF DESCRIPTION OF TI-IE DRAWINGS FIG. 1 illustrates a system comprising a central control unit and two chains of zone control units and their physical ar rangement for controlling the irrigation of two remote zones or areas such as those which might be found at a golf course;

FIG. 2 is a block diagrammatic representation of a central control unit and several chains of zone control units to show the variety of arrangements which can be achieved with the system ofthe present invention;

FIG. 3 is a fragmentary elevation of the face of the central control unit and illustrates primarily the various switches and indicator knobs for selecting the days of the week and the hours ofthe day when starting signals are to be sent to particular zone control units;

FIG. 4 is a fragmentary elevation of the face ofa zone control unit, again to show by reference to its indicator and selector knobs the manner in which a multicycle valve actuating schedule may be set;

FIGS. 5a and 5b are general block diagrams of a basic system incorporating features of the present invention and including a central control unit and a single zone control unit;

FIGS. 60 and 6b are schematic diagrams of the central control unit illustrated in block form in FIGS. 5a and 5b;

FIGS. 7a and 7b are schematic diagrams of the zone control unit shown in block form in FIGS. 5a and 5b FIGS. 80, 8b, and 8c illustrate the operation of the motor control portion of the central control unit whereby the day change motor is caused to advance by one day at midnight;

FIG. 9 is a schematic diagram of a signal transmission system including signal sensing and transmitting means in each of the central and zone control units for transmitting information between the units in opposite directions;

FIG. 10 is a series of waveforms to illustrate the operation of a circuit in the zone control unit which serves to generate a starting signal when the schedule selected for that zone control unit has been completed;

FIG. 1] is a block diagram to illustrate the wiring between the central control unit and a series of zone control units in a chain of such units;

FIG. 12 is a side elevation of an assembly in the zone control unit which is used to time the successive actuation of valves by the unit;

FIG. 13 is a plan view taken along line 13-13 of FIG. 12 and illustrating one side ofa wafer switch forming part of the timing assembly shown in FIG. 12;

FIG. 14 is a view of the same wafer switch taken along line 14-14 of FIG. 12 to illustrate that part of the switch which is used to control the resetting of the timing assembly.

E. DESCRIPTION OF AN EXEMPLARY SYSTEM INCORPORATING THE INVENTION l. Typical Application of the System The general layout of an area whose irrigation might be com trolled by the system of the present invention, is shown in FIG. I. It is shown to comprise a number of zones, such as zones 1 and 1a and zones 2 and 2a, with the irrigation of each zone being controlled by an individual zone control unit which is physically located near the zone which it controls and remotely from a single central control unit which, in the case ofa golf course, would usually be located near the club house. Also near the central control unit is a pump from which water lines extend to the valves at the various zones. Referring to zone 1 in particular, it is seen to be irrigated through a number of sprinklers which are arranged in five stations. Each station comprises a number of individual sprinklers which are controlled by means of a single valve which receives actuating signals from the zone control unit associated with zone 1. Zone control units 1, which serves to control the valves associated with the five stations of zone 1, is connected through a set of wires to the central control unit and it is over this set of wires that a starting signal is sent from the central control unit to the zone control unit 1 at selected hours of selected days. The zone control unit causes successive ones ofthe five valves at the five stations ofzone 1 to be actuated serially for selected periods of time in accordance with a preselected schedule.

The zone control unit I is also connected to the zone control unit la through a set of wires so that the latter zone control unit may be triggered by a starting signal generated by zone control unit 1 when that zone control unit has completed its assigned schedule of operations. When this occurs, the set of valves located in zone In is actuated in a similar manner to that described with reference to zone 1 under the control of zone control unit la.

A moisture-sensing device, called a tensiometer and labeled T in FIG. I, may be optionally provided to terminate a watering schedule being run by the zone control unit 1 if there is excessive moisture in zone 1. This will also serve to keep the zone control unit In from initiating its assigned schedule Normally, at aselected hour of a selected day a starting signal is sent to zone control unit-1, and in response to that signal the valves at the five stations of zone 1 are successively actuated through one or more cycles in accordance with a schedule set up on the, zone control unit. When .this schedule is completed, a starting signal issent from zone control unit 1 to zone control unit la and the valves .at the stations located in zone la are similarly actuated in accordance with the schedule under the control of zone control unit 1a. In a similar manner, a starting signal is sent by the, central control unit independently to zone control unit -2 so that the valves in zone 2 and the valves in zone 2a are sequentially actuated under the control of the chain which includes zone control units 2 and 2a. Information is sent back from all of the zone control units to the central control unitat all times to indicate the actuation of any valve in the zones shown.

The central control unitactuates the pump station whenever it receives a signal from the zonecontrol units indicating that a valve has been actuated. It will be noted that, by placing the zone control unitsnear the zones which they control, a significant saving in wire length is achieved over the type of system in which each of the valves is connected by wires to a single central control unit. Moreover, a saving in wire length is also achieved over that type of a system in which zone control units are used, but in which each of the zone control units is connected individually to a .single central control unit. Moreover, it is seen that as a result of the chain" concept, under which several zone control units are actuated in succession, each in response to a signal from a previous one in the chain, the simultaneous actuation of a large number of valves is avoided, thereby permitting the use of a smaller pump and smaller conduits leading to and from the pump. Thus, the system of the present invention serves not only to reduce system cost by modularization, it also serves to reduce the cost of electrical and hydraulic connections. 2. Possibilities of the Series Start Feature The irrigation system shownin FIG. 1 is a very simple example of what may be achieved with the series start feature, whereby successive zone control units in a chain are each acmated by the preceding zone control unit in that chain. FIG. 2 illustrates, in block form only, a more complex system to give a further illustration of how such a system andits components may be arranged. lt is seen to comprise a central control unit I] and a number of zone control units 13, each of which receives a starting signal over an individual one of six output lines from the central control unit ll. Of the first ofthe zone control units, 13a is partrof a chain of four serially connected zone control units, the first and last of which each have 11 outputs, successively to actuatell valves and the second and third of which each have five outputs, similarly to actuate five control valves as shown in FIG. 1. The third control unit in the chain is associated witha moisture-sensing device 17 so that the watering schedule controlledtby it and-by the subsequent zone control unit may be terminated in response toexcessive ground moisture sensed by the device 17. The second zone control unit, 13b in the top row is not part of a chain and is the only such unit actuated either directly or indirectly as a result of astartingsignal on the second of the output lines 15 from the central control unit 11.

The third of the output lines 15 is connected to apply a starting signal to a zone control unit 130 which is part of a chain having two zone control units 13c and 130-1 connected to operate in series succession. Additionally, two zone control units 13c-2 and l3c-3 are connected to the output of the second zone control unit l3c-l to initiate their respective schedules in response to a starting signal from that unit. Finally, two more zone control units, 13c-4 and -5 are connected to initiate their respective schedules in response to a starting signal from the zone control unit 13c-2. The arrangement of the other zone control units in FIG. 2 is selfevident and will not be described further. It will be noted that a single start signal from the central control unit 11 may be operative to initiate a single schedule, as in the case of the zone control unit 13b. Alternatively, the central control unit 11 may be operative to initiate the execution of a large number of schedules. Each of these schedules may occur by itself after a preceding schedule has been executed, as in the case of the chain including the zone control units 13a through l3a-3. Alternatively, two or more schedules may be in progress at the same time, as in the case of the zone control units 130-2 and 130-3.

3. Selecting a Particular Set of Schedules and Schedule-Starting Times In a preferred embodiment of the invention the central control unit 11 includes six channels, each of which is operative to generate a starting signal on a different one of the six output lines 15 to initiate a schedule of valve actuations in a difierent one of six zone control units. A portion of the central control unit panel associated with the first two channels of the unit is shown in FIG. 3. In essence, the central control unit includes a time generator, whose status is represented by the position of a pair of indicator knobs l9 and 21, and a set of switches, one set for each channel, for selecting the time of day and the day of the week when starting signals are to be produced. The hour knob 21 rotates against a dial 22 and completes one revolution every 24 hours. The day knob 19 rotates intermittently opposite a day index dial 20 and is advanced one position every time the hour knob 21 completes one of its revolutions. The day index dial 20 has 14 positions, one position for each day of a fortnight so that a total cycle of its knob 19 takes 2 weeks to complete. In practice, the day and hour knobs l9 and 21 are adjusted for the existing time of the existing day, following which these knobs will be advanced in synchronism to indicate the correct day and the correct hour by a mechanism which will be described subsequently.

Referring only to the panel portion marked Channel 1," since the remaining channels are identical, it includes a series of hour selector switches 23 and a series of day selector switches 25. There is one hour selector switch 23 for each of the 24 hours of the day, and a day selector switch 25 for each of the 14 days of the 2 weeks covered by the day index knob 19. The switches 23 and 25 control the days of the week and the times of the day when a starting signal is to be produced by the central control unit 11 on one of its outputs. If, for example, it is desired that such starting signals are to be produced on the output corresponding to channel 1 on Monday, Wednesday, and Friday at 6 arm. and 6 pm, the s-"ches 25 for Monday, Wednesday, and Friday of both weeks and the starting hour selector switches 23 and 25 for 6 am. and 6 pm. are all placed in their ON positions.

Each starting signal produced at the output of channel 1 is operative to initiate a schedule of value actuations at the particular zone control unit 13 to which the starting signal is applied. A large variety of such schedules may be selected by means of the control knobs on the face of the zone control unit 13 which is shown in FIG. 4. The zone control unit includes as its principal component a switching means which is stepped through a number of states or positions in succession in response to a starting signal from the central control unit. The particular state, or position, of the switching means is indicated on the face of the zone control unit by the station index, comprising a station index knob 27 which turns against a station index dial 29. Many arrangements are possible for the station index dial 29, depending upon the type of schedule which is to be selectable with the zone control unit. The par ticular arrangement shown in FIG. 4 is for four successive cycles of valve actuations during a single schedule. During each of the four cycles, the switching means and its associated knob 27 move through five positions, and in each of those positions a respective one of five valves is actuated. Moving clockwise around the station index dial 29, the knob 27 is subsequently stepped through second, third, and fourth cycles, during each of which the same five valves are again actuated. A delay position is also provided between the four cycles. When the knob 27 is in a delay position, none of the valves is actuated. The knob 27 and its associated switching means remain at each of the positions around the dial 29 for a variable period of time controlled by a set of time delay selector knobs 31 on the face of the zone control unit, there being one knob for each position on the station index dial 29. Each knob 31 is set against a dial 32 having a series of positions for time delays of 2, 5, 10, 15, 20, 25, 30, 35, 40, 50, and 60 minutes respectively.

The time delay selector knobs 31 are arranged in four rows, one row for each cycle of the station index. Each row has five knobs 31, corresponding to the five positions of the station index dial 27. Each of the first three rows of knobs also includes a knob 31a for selecting the length of time for which the station index knob 27 is to remain in a particular one of the three delay positions. The particular settings of the time delay selector knobs 31 and 31a shown in FIG. 4 illustrates one of the many schedules which may be selected for the actuation of a set of five valves. During the first cycle, the first two valves are actuated for minutes each and the third, fourth, and fifth valves are actuated for minutes each. A delay of zero duration is selected between the first and second cycles so that the actuation of the fifth valve is followed without delay by the second cycle, during which the first two valves are actuated for 5 minutes each and the last three valves for 10 minutes each. This is followed by a 5 minute delay to allow the irrigated area to absorb the distributed water, after which the third cycle begins, during which each of the five valves is actuated for 5 minutes. This is followed by a 2 minute delay, following which the fourth cycle is executed, during which each of the five valves is actuated for 2 minutes. After the actuation of the last valve during the fourth cycle, the knob 27 and its associated switching a schematic are returned to their OFF position, and the schedule of the zone control unit is complete.

4. Organization and Operation of the Exemplary System a. Introduction A system comprising a single zone control unit 13 and a corresponding channel of the central control unit 11 is shown in block diagram form in FIG. 5. The schematic diagram of the same system appears in FIGS. 6 and 7, which should be assembled from left to right in the order 60, 6b, 7a, 7b. FIG. 7 is a schematic diagram of the zone control unit 13. FIG. 6 is a schematic diagram of a single channel of the central control unit 11 and additionally shows the remaining five channels of the unit in block diagram form. In describing the system shown in FIGS. 5, 6, and 7, what will be explained first are the basic components of the zone control unit 13 and the central control unit 11 which comprise the basic system for initiating and executing a schedule of valve actuations. Following this description, certain auxiliary features of the invention, carried out in some instances by components in the central control unit, in other instances by components in the zone control unit, and still in other cases by a combination of components in both of the units, will be described.

b. The Control Section of the Zone Control Unit I. In General Basically, it is the function of a zone control unit 13 successively to actuate selected ones of a plurality of valves for selected time intervals in response to an externally produced signal. This function is achieved by a control section 32 (FIG. 5b) which includes a switching means 33 having a rest state, a plurality of intermediate states, and a plurality of outputs connected to cause power to be applied to respective ones of the valves during successiveones of the intermediate states of the switching means. Stepping means 49 and 45 are provided to advance the switching means by one state in response to suecessive control signals. An initial control signal is applied to the stepping means by a start signal sensing means 139 in response to one of the externally produced starting signals so as to cause the switching means 33 to be advanced from its rest state to its first intermediate state. Following this, a delayed control signal is applied to the stepping means 49 by a timing control circuit 89 in response to each advancement of the switching means 33 to one of its intermediate states. In this way, following a starting signal, the switching means 33 is caused to spend a certain period of time in each of its intermediate states before being stepped onto its next intermediate state. During selected ones of these periods a respective one of the valves is actuated.

2. Stepping the Valve Control Wafer Switch In FIG. 7b the switching means is shown as a wafer switch 33 which includes a phenolic rotor having a conductive ring 35 thereon. A stationary wiper 37 applies power to the ring 35, and a tab 39 extending from the ring 35 engages a series of 20 stationary wipers 41 around its periphery. The wipers 41 are arranged in four groups of five wipers corresponding to the four cycles of valve actuation discussed with reference to FIG. 4. Successive ones of the five wipers in each of the four groups are connected to respective ones of five valves 43. In addition to the states, or positions, of the wafer switch 33 in which its tab 39 engages one of the wipers 41, it also has a rest, or OFF, position between the set of wipers associated with the fourth and first cycles, and three delay positions, one between each of the set of wipers 41 associated with the first, second, third and fourth cycles. When the wafer switch 33 is in its rest position, orin one of the delay positions it does not engage any of the wipers 41 and no power is applied to any of the valves.

The wafer switch 33 is advanced from its rest position through its intermediate positions and back to its rest position again by means of a 1 rpm. station position motor 45 through an output shaft 47, under the control of a motor control 49. Together, the motor 45 and the motor control 49 comprise the means for stepping the wafer switch 33 by one position in response to a control signal applied to the motor control 49. The motor control 49 includes a relay 51 having an armature with two sets of contacts 53 and 55. The contacts 55 close when the relay 51 is energized in response to a control signal being applied to its coil over a lead 59 through a manual-auto switch 61, which is normally in its auto position, as shown. With the switch 61 in its manual position, the wafer switch 33 may be set manually by means of the knurled index knob 27 (FIG. 4) which is also keyed to the shaft 47.

The contacts 55 of the relay 51 are connected in series between the station position motor 45 and a source of AC power, labeled E. This power is received in the zone control unit over a pair of leads 61 and 63 from a power supply in the central control unit 11. The leads 61 and 63 are shown in FIG. 7a as part of a power supply 64 in the zone control unit 13. They are directly connected to several circuits in the zone control unit 13. To reduce the nt. ber oflines in the drawings, all of these connections are not shown as linz Instead, the leads 61 and 63 are labeled E and C respectively, and a similar label is applied to any circuit point which is connected to them. Since the C line 63 serves as ground, a ground symbol is also used to indicate that a circuit point is connected thereto.

The AC voltage across the lines 61 and 63 is converted into half-wave rectified DC by means of a diode 68 and a capacitor 70 connected in series across the lines in the power Supply 64. Their junction is labeled 13+ and circuits through which DC is to be driven are connected across the points C and 8+ of the power supply 64. When a control signal is first applied to the motor control relay 51, a circuit is completed through its contacts 55 across the power supply lines 61 and 63 through the station position motor 45, causing it to turn the rotor of the wafer switch 33 clockwise from its initial position.

The motor control 49 also includes means to keep the motor 45 energized long enough to advance the valve control wafer switch 33 by one step to its next intermediate position. For this purpose another wafer switch 65 is mounted on the shaft 47 of the station position motor 45, having a conductive ring 66 with a series of alternate notches 67 and tabs 69 thereon. The conductive ring is in continuous contact with a stationary wiper 71 and in intermittent contact with another stationary wiper 73 through its tabs 69. The first stationary wiper 71 is connected to a switched B+ line 75 to which B+ DC voltage is supplied from the zone control power supply 64 through a DC power control wafer 77. The DC power control wafer 77 is a third wafer switch mounted on the output shaft 47 of the station position motor 45 and serves to switch DC power to the line 75 as soon as the station position motor 45 has turned the valve control wafer switch 33 from its initial position. For this purpose the wafer switch 77 is provided with a conductive ring 79 having a single notch 81, a first stationary wiper 83 in continuous contact with the ring 79, and a second stationary wiper 85 which is in contact with the ring 79 at all times except when it is opposite the notch 81. This is arranged to occur when the valve control wafer switch 33 is in its rest, or OFF, position.

When the station position motor 45 has begun its advance in response to the application of a control signal to the motor control 49, a circuit is closed from the B+ output of the power supply 64 through the DC power control wafer switch 77, the switched B+ line 75, and through the motor control wafer switch 65 which is now closed, to its stationary wiper 73. This 8'' voltage is applied to the motor control relay 51 through a diode 87 connected between the stationary wiper 73 and the coil of the relay, energizing the latter. Consequently, the motor 45 continues to be energized independently from the continued presence of the control signal which had initiated its movement. This movement continues until the circuit through the motor control relay 51 is broken by the motor control wafer switch 65. This occurs when the particular tab 69 of the switch 65 which had been in engagement with the output wiper 73 of the switch moves out from under the wiper and is replaced by one of the notches 67. The wafer switch 65 is so oriented on the motor shaft 47 that its notches 67 are in registry with the stationary wipers 41 of the valve control wafer switch 33, so that each time that the tab 39 of the wafer switch 33 engages one of the wipers 41 of switch, i.e. each time the switch reaches a new position, the motor control wafer switch opens and brakes the switched B+ circuit to the motor control relay 51. As a result, the motor 45 is automatically deenergized, due to the opening of the circuit to the motor control relay 51, after the motor has advanced the valve control wafer switch 33 by one position.

3. Producing a Variable Delay for Stepping the Switch As stated at the beginning of this section, a delayed control signal is applied to the stepping means, i.e. the motor control 49 and the motor 45, in response to each advancement of the valve control switching means 33 to one of its intermediate states. This function is performed by the elapsed time control 89. Generally, the elapsed time control 89 includes a wafer switch 91, a set of time selector switches 93, timing and reset wafer switches 97 and 99, both driven by timing and reset motors 101 and 103, and a relay 105. The physical arrangement of the timing and reset wafer switches 97 and 99, and their motors 101 and 103 is shown in FIGS. 12, 13, and 14, and will be discussed later. The wafer'switch 91 ismounted on the station position motor shaft 47 coaxially with the other wafer switches 33, 77, and 65 and has one position corresponding to each of the intermediate positions of the valve control wafer switch 33. It includes a conductive ring 107 having a single tab 110 which makes contact with successive ones of a series of stationary wipers 111 in successive ones of the positions of the wafer switch 91. Through a wiper 109 the conductive ring 107 is in continuous contact with the motor control relay 51 to which the wiper 109 is connected through the manual-auto switch 61 and a connecting line 112.

Each of the contacts 110 of the wafer switch 91 is connected to the wipe of a different one of the set of time selector switches 93. While only three time selector switches 93 are shown in FIG. 7, there are actually 23 of them, one for each position of the wafer switch 33. Each of the time selector switches 93 is controlled by one of the control knobs 31, 310 on the panel of the zone control unit 1 1 (FIG. 4), and each has a series of stationary contacts 94 with which the movable contact of the switch may be engaged. There are eleven contacts 94, labeled 0, 2, 5, l0, 15, 20,25, 30, 35, 40 and 50 for selecting delays of from 0 to 50 minutes. The switches also have a blank position between the 50-minute and 0-minute contacts, 0 when a 60 minute delay is desired. On every one of the time selector switches 93, successive ones of the 2-minute through SO-minute stationary contacts 94 around the periphery of the switch are connected to corresponding stationary wipers 114 around the periphery of the timing wafer switch 97. The 0- minute contacts 94 of all of the selector switches 93 are connected to 8+ through a common conductor 108. The 60 minute wiper 114 of the timing wafer switch 97 is connected directly to the line 1 12.

In addition to its set of stationary wipers 114, the timing wafer switch 97 also includes a rotor carrying a conductive ring 113 to which 8+ is normally applied by a stationary input wiper 116. The ring 113 has a tab 115 which engages successive ones of the stationary wipers 114, and applies B+ voltage to them as the rotor is turned. The rotor is mounted on a shaft 117, which is turned by both the timing motor 101 and the reset motor 103, depending upon which one of those motors is energized. The timing motor 101 is energized at the instant when the valve control wafer switch 33 has been advanced to a new position, and it turns the rotor of the timing wafer switch 97 at a rate of one revolution per hour until it is deenergized, which occurs when the switch 33 is moved from its new position. The reset motor 103 is energized at this time and returns the switch 97 to its rest position at a rate of l revolution per minute. When this is accomplished the reset motor 103 is also deenergized.

As seen in FIG. 12, the timing and reset wafer switches 97 and 99 are part of a single rotary phenolic switch assembly 120, having a stator member 122 bolted to a U-shaped bracket 124 and a rotor member 118 turned within the stator member by the shaft 1 17. The timing and reset motors 101 and 103 are mounted on opposite arms of the bracket 122. The timing switch 97 is carried on one side of the switch assembly (FIG. 13) and the reset switch 99 is mounted on the other side (FIG. 14). Thus, the two switches 97 and 99 are always turned in the directions indicated in FIGS. 13 and 14 in unison through the shaft 117 by either the timer motor 101 or the reset motor 103. The motors are provided with clutches 126, 128 so that each of them may turn the shaft 117 without being hindered by the other. As best shown in FIG. 13, stationary wipers 114 of the timing switch 97 are so distributed around the periphery of its conductive ring 113 that successive ones ofthem are contacted by its tab 115 after 2, 5, 10, 15,20, 25, 30, 35, 40, 50, and 60 minutes respectively.

Let it be assumed that the more 45 has just advanced the wafer switch 33 to a new position. If it is to advance again without delay, the time selector switch 93 corresponding to that position is set to engage its 0-minute contact 94. This places B+ on the line 112 as soon as the new positio. is reached and the motor control relay 51 is energized, without delay. If the switch 33 is to be left in its new position for anywhere from O to 50 minutes, the appropriate time selector switch 93 is set to the desired delay position where its wiper engages a selected one of the contacts 94. When the requisite time has elapsed, the timing wafer switch 97 will close a path from 8+ to the selected contact of the switch 93 and through it to the line 112 to energize the motor control relay 51. To select a 60 -minute delay for a given position of the switch 33, the corresponding timing switch is set on its 60-minute position so that a path is not established from B+ to the line 112 until the timing wafer switch 97 has been turned to where a circuit is made between its wipers 116 and 60-minute wiper 114, the latter of which is directly connected to the line 112.

For proper operation of the elapsed time control 89 it is necessary that the timing motor 101 be started at the instant when the valve control wafer switch 33 has been advanced to one of its intermediate positions, provided however that the timing wafer switch 97 is in its starting position. For this reason, the timing motor 101 is connected across the outputs E and'C of the power supply 64 through contacts 119 of the relay 105 and through contacts 121 of a relay 123 in the AC power control 125 only when the elapsed time control relay 105 is deenergized and when the AC power control relay 123 is energized. The AC power control relay 123 is energized by the switched B+ through the DC power control wafer switch 77 during all of the time that the valve control wafer switch 33 is away from its initial position. Under these circumstances, by means to be described next, the elapsed time control relay 105 is energized with B+ voltage from the line 75 through the motor control wafer switch 65 and through the reset wafer switch 99 unless the switch 33 is in one of its intermediate positions AND the timing wafer switch 97 is in its initial position. Only if the latter two conditions exist can the relay 105 be deenergized and therefore only then will the timing motor 101 start.

The reset motor 103 is connected through the common shaft 117 to the rotors of both the timing wafer 97 and the reset wafer 99 and is energized by means of the contacts 119 when the relay 105 is energized, provided that the AC power control relay 123 is also energized at that time. This will be the case whenever the valve control switch 33 is away from its initial position. The principal function of the reset wafer switch 99 is to control the energization of the reset motor 103 through contacts 119 of the time control relay 105. Its principal part is a ring 129 carried by the rotor 118 of the switch assembly 120 (FIG. 13), and having a single notch 131. A pair of stationary wipers 133 and 135 are maintained in electrical contact with one another through the ring 123, except when the wiper 135 is in the notch 131. A diode 127 connects the.

output wiper 73 of the motor control wafer switch 65 to the wiper 133 of the reset wafer switch 99, closing a circuit from the switched B+ line 75 through the wafers 65 and 99 to the coil of the relay 105 whenever the wafer switch 99 is closed.

It will be helpful at this point to explain the operation of the elapsed time control 89. Let it be assumed that the valve control wafer switch 33 is in its initial OFF position and that the reset wafer switch 99 is open. Let it be assumed next that an initial control signal has been applied to the motor control relay 51 so as to energize the station position motor 45. Under these circumstances the motor shaft 47 will turn switch 33 from its OFF position toward its first intermediate position, in which it will engage the first of the stationary wiper contacts 41. The shaft 47 will also turn the DC power control wafer switch 77 and the motor control wafer switch 65.

Closure of the DC power control wafer switch 77 has the effect of energizing the AC power control relay 123 and therefore of energizing the timing motor 101 through the contacts 121 of that relay. Since the reset wafer switch 99 is open, the relay 105 is not energized and therefore its contacts 119 are in a position to complete the circuit to the timing motor 101. The timing motor 101 begins to run and, through its shaft 117, turns the rotor of its timing wafer 97 past its stationary wipers 114 until the tab 115 engages a wiper which is in contact through one of the time selector switches 93 and through the time control wafer switch 91 with the input line 59 to the motor control 49. When this happens, the motor control relay 51 is energized from the B+ voltage source 64 through contacts 137 of the relay 105 and the station position motor 45 is again energized and begins to turn its associated wafer switches to their next respective positions. This causes the motor control wafer switch 65 to close, so as to apply the switched 13+ voltage through the diode 87 to the relay 51, thereby continuing to energize the station position motor 45 independently of the control signal produced by the elapsed time control.

The closing of the motor control switch 65 also has the effeet of applying the switched 13+ voltage through the diode 127 to the reset wafer switch 99 which, having been closed by the operation of the timing motor 101 during the timing sequence of the elapsed time control 89, completes a circuit to the coil of the time control relay 1105, thereby energizing it. This reverses the state of its associated contacts 1 19 and 137, Reversal of the state of the contacts 137 has the effect of removing the 13+ voltage from the timing wafer switch 97 and latching the relay 105 through the reset wafer switch 99. Reversal of the contacts 1 19, on the other hand, has the effect of transferring the E voltage from the timing motor 101 to the reset motor 103, which proceeds to drive both the reset wafer switch 99 and the timing wafer switch 97 back to their initial position, in which the reset wafer 99 opens and deenergizes the relay 105 and, through the resulting reversal ofits contacts 119, also deenergizes the reset motor 103. The timing motor 101 is not reenergized at this time because, by the time the elapsed time control 89 has been reset, the station position motor 45 will have driven its associated wafer switches to their next respective positions in which the motor control wafer switch 65 is again open and, therefore, in which the switched B+ voltage is cut off from the reset wafer switch 99. At this time the valve control wafer switch 33 and the time control wafer switch'91 are both in their first intermediate positions, in which their tabs 39 and are in contact with the first ones of the stationary wipers 31 and 111 respectively. With the valve control wafer switch 33 in its first intermediate position, the motor control wafer switch 65 is again open and the timing motor 101 is again energized through the contacts 119 of the time control relay 105, thereby initiating another time delay cycle in the elapsed time control unit.

The successive advancement of the valve control wafer switch 33 by control signals which are applied to the motor control 49 by the elapsed time control 89 after a predetermined delay time is repeated until the switched 33 is returned to its initial or OFF position, at which time the DC power control wafer switch 77 opens, cutting off the 13+ voltage from all of the circuits which are energized by the switched 13+ voltage over the line 75, including the AC power control relay 123. With its contacts 121 in the released position, the E voltage is no longer applied to either of the timing motor 101 or the reset motor 103 so that the elapsed time control unit 89 is deactivated, since no further control signals are applied over the line 112 to the motor control 19 until another schedule is initiated by a control signal over the line 59.

4. Initiating a Schedule in Response to a Starting Signal The initial control signal, which serves to cause the station position motor 45 to move the valve control wafer switch 33 away from its OFF position, is generated by a start signal sensor 139 in response to a starting signal from the central control unit 11. interposed between the central control unit 11 and the start signal sensor 139 is a blocking circuit 141, whose function is to disable the start signal sensor 139 when the valve control wafer switch 33 has left its rest position in response to a given starting signal and to kee "we start signal sensor 139 disabled so long as that starting signal persists. 1r his way the blocking circuit 141 prevents the same starting signal from initiating more than one schedule in the zone control unit. Briefly, the blocking circuit includes a relay 143 having a r -t of contacts 145 which close a circuit for a starting signal from the central control unit 11 to the coil ofa relay 147 in the start signal sensor 139. The relay 147 has tw sets of contacts 149 and 151.

Once it is energized by a starting signal from the central control unit 11, the relay remains energized by means of a latching circuit from ground, through-a diode 148, contacts 151 of the relay 147, contacts 145 of the blocking circuit relay 143, and through the coil of the start sensor relay 147 to the E voltage terminal. While it is energized, the relay 147 applies a B+ voltage through its contacts 149 and through a diode 150, to the motor control 49, this being the control signal which is produced by the start signal sensor 139 in response to the starting signal from the central control unit 11. As explained 

1. Apparatus for programming the cyclic actuation of a plurality of valves for selected time intervals on selected days of the week at selected hours of the day, comprising in combination: a. a central control unit for generating starting signals at selected hours of selected days; b. a chain of at least two individual zone control units, each responsive to a starting signal successively to actuate selected ones of a respective set of valves for selected periods of time in accordance with a preselected schedule, and each generating a starting signal when the selected actuation of the last of its associated set of valves has been completed; c. means for applying the starting signal from said central control unit to the first zone control unit in said chain; and d. means for applying the output signal from said first zone control unit to the next zone control unit in said chain, so that successive zone control unit sand their associated valves are actuated in response to the completion of a schedule by the preceding zone control unit in said chain.
 2. Apparatus in accordance with claim 1 and characterized further by a. means in each zone control unit in said chain for producing a monitor signal while that zone control unit is in operation; b. display means in said central control unit for producing an indication in response to said monitor signal; and c. means at each said zone control unit for relaying said monitor signal from the next succeeding zone control unit to the preceding zone control unit in the chain so that said display means is made to respond to the operation of each of said zone control units.
 2. means for applying power to said motor in response to a given control signal while said rotary switch is in a given one of its positions and continuing to apply power until said rotary switch reaches its next position.
 3. In an irrigation system wherein water is supplied unDer pressure by means of a central pump to a plurality of remotely located valves, a pump and valve control system comprising in combination: a. a central control unit for generating starting signals at selected hours of selected days and having a pump control unit for controlling power to said central pump; b. at least one remotely located zone control unit responsive to a starting signal successively to actuate selected ones of a set of valves for selected periods of time, said zone control unit having means for generating a pump-actuating signal while any of said set of valves is being actuated; c. means for transmitting said starting signals to said zone control unit; and d. means for transmitting said pump-actuating signal to said pump control unit so that said pump shall become actuated when any of said valves is actuated.
 4. Apparatus for programming the cyclic actuation of a set of valves for selected time intervals on selected days of the week at selected hours of the day comprising in combination: a. a central control unit for generating starting signals at selected hours of selected days; b. a remotely located electrically powered zone control unit responsive to a starting signal from said central control unit to actuate said set of valves in accordance with a preselected program; c. power supply means in said central control unit; d. means for transmitting the output of said power supply means to said zone control unit; e. means in said zone control unit for terminating a partially executed program in response to the interruption and subsequent resumption of electric power; and f. means in said central control unit for manually interrupting the supply of electric power to said zone control unit, thereby to permit manual termination of a partially executed program.
 5. The apparatus of claim 4 characterized further by rain switch means in said control unit associated with an external rain sensor for preventing said central control unit from generating starting signals and for momentarily interrupting the supply of electric power to said control unit automatically when said rain sensor detects rain.
 6. In an irrigation system wherein water is supplied under pressure by means of a central pump to a plurality of remotely located valves, a pump and valve control system comprising in combination: a. a central control unit; b. a remotely located zone control unit; c. a pair of wires connecting said units; d. an alternating current source in said central control unit connected in series with one of said wires; e. means in each unit for sensing current flow through said wires in a respective one of mutually opposite directions; f. switching means in each unit for completing a respective circuit through said wires and through the sensing means in the other unit, the circuit completed by the switching means in a given unit being capable of carrying current only in the direction sensed by the sensing means in the other unit; g. means in said central control unit for closing its switching means at selected hours of selected days; h. means in said zone control unit for successively actuating selected ones of a set of valves for selected periods of time in accordance with a preset schedule in response to the detection of current by its sensing means; i. means in said zone control unit for closing its switching means while any of said set of valves is being actuated; and j. means in said central control unit for actuating said central pump in response to the detection of current by its sensing means.
 7. The apparatus of claim 6 characterized further by a. a third wire connecting said alternating current source to said zone control unit; b. control means in said zone control unit powered by current from said alternating current source through said third wire and through the wire which is in series with said alternating current source and responsivE to the interruption of said current to abort a schedule in progress when said current is reapplied; and c. means in said central control unit for interrupting the supply of said current to said control means.
 8. In apparatus for programming the cyclic actuation of a plurality of valves for selected time intervals on selected days of the week at selected hours of the day, the combination comprising: a. a central control unit; b. a remotely located zone control unit; c. a pair of wires connecting said units; d. an alternating current source in said central control unit connected in series with one of said wires; e. means in each unit for sensing current flow through said wires in a respective one of mutually opposite directions; f. switching means in each unit for completing a respective circuit through said wires and through the sensing means in the other unit, the circuit completed by the switching means in a given unit being capable of carrying current only in the direction sensed by the sensing means in the other unit; g. means in said central control unit for closing its switching means at selected hours of selected days; h. means in said zone control unit for successively actuating selected one of a set of valves for selected periods of time in accordance with a preset schedule in response to the detection of current by its sensing means; i. means in said zone control unit for closing its switching means while said schedule is in progress; and j. means in said central control unit for indicating that said schedule is in progress in response to the detection of current by its sensing means.
 9. In an irrigation system wherein water is supplied under pressure by means of a central pump to a plurality of remotely located valves, a pump and valve control system comprising in combination: a. a central control unit; b. a remotely located zone control unit; c. a pair of wires connecting said units; d. an alternating current source in said central control unit connected in series with one of said wires; e. means in each unit for sensing current flow through said wires in a respective one of mutually opposite directions; f. switching means in each unit for completing a respective circuit through said wires and through the sensing means in the other unit, the circuit completed by the switching means in a given unit being capable of carrying current only in the direction sensed by the sensing means in the other unit; g. means in said central control unit for closing its switching means at selected hours of selected days; h. switching means in said zone control unit for successively connecting selected ones of said valves to a current source of selected periods of time in accordance with a preset schedule in response to the detection of current by its sensing means; i. load simulator means in said zone control unit for connecting a dummy load to said current source between the successive connections of valves thereto; j. means in said zone control unit for closing its switching means in response to current from said current source; and k. means in said central control unit for actuating said central pump in response to the detection of current by its sensing means.
 10. In an irrigation system wherein water is supplied under pressure by means of a central pump to a plurality of remotely located valves, a pump and valve control system comprising in combination: a. a central control unit; b. a remotely located zone control unit; c. a pair of wires connecting said units; d. an alternating current source in said central control unit connected in series with one of said wires; e. first and second sensing means in said central control unit for sensing current flow through said wires in a given direction, said first and second sensing means being responsive to current flow at first and second duty cycles respectively; f. third seNsing means in said zone control unit for sensing current flow through said wires in the opposite direction; g. switching means in said central control unit for completing a circuit through said wires and through said third sensing means capable of carrying current only in the direction sensed by third sensing means; h. second and third switching means in said zone control unit, each for completing a circuit independently of the other through said wires and through said first and second switching means for carrying current in the direction sensed by said first and second sensing means; i. means in said central control unit for closing its switching means at selected hours of selected days; j. means in said zone control unit for successively actuating selected ones of a set of valves for selected periods of time in accordance with a preset schedule in response to the detection of current by said third sensing means; k. means in said zone control unit for closing said second switching means at said first duty cycle while any of said set of valves is being actuated; l. means in said zone control unit for closing said third switching means at said second duty cycle while said schedule is in progress; m. means in said central control unit for actuating said central pump in response to the detection of current by said first sensing means; and n. means in said central control unit for producing an indication that said schedule is in progress in response to the detection of current by said second sensing means.
 11. In a zone control unit for successively actuating selected ones of a plurality of valves for selected time intervals in response to an externally produced starting signal, the combination comprising: a. switching means having a rest state, a plurality of intermediate states, and a plurality of outputs connected to cause power to be applied to respective ones of said valves during successive ones of said intermediate states; b. stepping means for advancing by one the state of said switching means in response to successive control signals; c. start signal sensing means for applying an initial control signal to said stepping means in response to one of said starting signals so as to cause said switching means to be advanced from its rest state to its first intermediate state; and d. timing means for applying a delayed control signal to said stepping means in response to each advancement of said switching means to one of its intermediate states.
 12. A zone control unit in accordance to claim 11 and further characterized in that a. said switching means includes a multiposition rotary switch connected to apply power to respective ones of said valves in successive ones of its positions; and b. said stepping means includes
 13. The zone control unit of claim 11 characterized further by signal-blocking means for disabling said start signal sensing means when said switching means leaves its rest state in response to a given starting signal and for keeping said starting signal sensing means disabled so long as said given starting signal persists.
 14. In a zone control unit for a set of valves wherein an externally generated starting signal causes selected ones of said set of valves to be actuated successively for individually selected time intervals during a first cycle, followed after a selected delay interval by a second cycle during which the successive actuation of said set of valves is repeated, the combination of: a. switching means having a rest position, a first series of valve positions, one position for each of said valves for controlling said first cycle, a delay position, And a second series of valve positions, one position for each of said valves for controlling said second cycle; b. means for actuating each of said valves while said switching means is in a position associated therewith; c. means for advancing said switching means in response to successive control signals; d. start signal sensing means for applying an initial control signal to said stepping means in response to one of said starting signals so as to cause said switching means to be advanced from its rest position to its first valve position; and e. timing means for applying an individually delayed control signal to said stepping means so as to advance it by one position a predetermined time after its advancement to each one of its valve and delay positions.
 15. The zone control unit of claim 14 characterized further by the provision of means responsive to a moisture indication by a tensiometer only during said delay interval to apply a control signal to said control means of sufficient duration to return said switching means to its rest position.
 16. In an electrically powered zone control unit for successively actuating selected ones of a plurality of valves for selected time intervals in response to an externally produced starting signal the combination comprising: a. electrical switching means having a rest state, a plurality of intermediate states, and a plurality of outputs connected to cause electric power to be applied to respective ones of said valves during successive ones of said intermediate states; b. means responsive to said starting signals for advancing said switching means from its rest state through successive ones of its intermediate states back to its rest state, leaving said switching means in each of its intermediate states for a selected time interval; and c. means responsive to the interruption and subsequent return of electric power to said zone control unit while said switching means is in one of said intermediate states for directly returning said switching means to its rest state. 